1. Field of the Invention
The present invention relates to an organic EL display device, and more particularly to an organic EL display device which can suppress the chromaticity irregularities and the brightness irregularities by reflecting a result of an analysis of film forming misalignment of an organic EL layer.
2. Description of the Related Art
Different from a liquid crystal display device, a display device which adopts organic EL elements (OLED) does not require a backlight and hence, the display device can realize the reduction of thickness and weight thereof. A color reproduction method of the organic EL element follows the additive color mixing theory based on emission of lights of three primary colors in the same manner as a conventional CRT. Blue(B), green (G) and red (R) dots (pixels: sub pixels in a full-color display) respectively emit lights, and the respective dots possess characteristic spectroscopies in the substantially same manner as the CRT.
The organic EL display device can be classified into a bottom-emission-type organic EL display device and a top-emission-type organic EL display device depending on extracting direction of emitted light. The bottom-emission-type organic EL display device has following advantages.
(1) A substrate can be manufactured using substantially same process as a thin-film-transistor-type liquid crystal display device.
(2) Cathodes in a film shape can be formed easily.
(3) Sealing can be also performed easily.
As a disadvantage of the bottom-emission-type organic EL display device has, an openings of each pixel is restricted attributed to the arrangement of a thin film transistor and hence, a numerical aperture becomes low.
On the other hand, in the top-emission-type organic EL display device, the pixel is not influenced by the arrangement of the thin film transistor and hence, the thin film transistor can be arranged in a pixel region whereby the numerical aperture becomes high. However, the cross-sectional structure of the pixel is complicated and hence, it is necessary to make a sealing can (sealing glass) have the light transmitting property.
Both types of the organic EL display device are constituted by providing a display panel which forms pixels constituted of a plurality of organic EL elements in a matrix array on an active substrate on which thin film transistors are formed and by assembling a peripheral member such as a drive circuit to the display panel. The organic EL element is provided to the active substrate for every unit color pixel which is constituted of a plurality of sub pixels, and is constituted of one electrode in which a sub pixel opening is formed, an organic EL layer which is formed on one electrode, and another electrode which is formed on the organic EL layer while covering the organic EL layer.
In the mass-producing process of the organic EL display devices, a vapor deposition method is often used to form the organic EL layer on the sub pixel opening. Japanese Patent Laid-Open No. 2003-297562 (Patent document 1) discloses a vapor deposition method of forming an organic EL layer on an organic EL panel by masking.